Fluid valves, whether for liquids or gases, necessarily have components exposed to fluid being restrained from flowing as would have occurred in the absence of any valving. Increased pressure of fluid so restrained makes added demands upon valve structures, stressing not only connectors, housing, and seals, but also whatever part(s) may be designed to close, adjust, or open the valve to flow.
Conventional valves have been modified to cope with the forces to be overcome, as by shielding components with sliding or rotary sleeves, building leverage into an individual valve, or cascading valves to enable a small valve to control a larger one. Proponents have characterized some of those configurations as balanced, such as in U.S. Pat. No. 3,425,448 to Peterson, for Fluid Pressure Balanced Valve, U.S. Pat. No. 3,658,450 to Woodling, for Balanced Fluid Pressure Valve Means, U.S. Pat. No. 4,190,231 to Vimercati, for Bilaterally Balanced Fluid Control Valve. Numerous valve-adjustment mechanisms are known, including cams, pivoted arms, and even rack-and-pinion devices, some of which are shown in U.S. Pat. No. 829,120 to Mumford, U.S. Pat. No. 2,074,701 to Lohmolder, and U.S. Pat. No. 4,260,128 to Tito. Electromechanical actuators are known and are often employed for their capability of applying considerable force and, in servo form, for their ability to hold any selected position, such as fully closed, any given intermediate setting, or fully open.
Notwithstanding the existing variety of fluid valves, there is a pressing need to render valve structure and adjustment simpler and more nearly independent of applied fluid pressure, rather than going on and on to greater complexity and sophistication in order to cope with requirements for increasing reliability, safety, and utility. This present invention of mine meets that need in a fundamental way.